The structure according to the present invention finds particular use in the finishing of large areas such as Portland cement concrete driveways which are ordinarily provided with a fine brush finish. In order to provide joints of weakness in the finished slabs the concrete is allowed to set up to a condition where wooden planks may be laid thereon for support of a finisher who manipulates a jointing tool for such purpose. Such operations take an inordinate amount of time and are extremely costly.
According to the present invention the surface of the concrete is finished by a long handled float, known in the trade as a bull float, and after being properly finished the float has affixed thereto a rigid elongated member which, when the float is manipulated, describes a line of weakness in the yet unset concrete. The member is part of an accessory which can be readily secured to or removed from the float.